Contact

John Ross's deep sea instruments (1818)

The plate comes from John Ross’s ‘A voyage of discovery:
made under the orders of the Admiralty, in His Majesty's ships Isabella and
Alexander, for the purpose of exploring Baffin's Bay, and inquiring into the
probability of a North-West Passage’, Vol.2, (2nd edition), 1819. Longman,
London. It depicts three instruments used by the expedition: a Deep
Sea Clam (Fig. 1), a Hydraphorus (Fig. 2) and a Marine Artificial Horizon (Fig.
3).

The Deep Sea Clamm was an early grab sampler
(sounder) designed by Sir John Ross (1777–1856) on board H.M.S. Isabella in 1818. Ross wrote: “The instrument was made from the model by the
ship’s armourer, and succeeded on the first trial”. The Clamm worked
well and collected sediment as well as some biota (worms, and starfishes
attached to the cable) from depths at over 1,000 fathoms. A bonus was that they
could, once the instrument was on deck, insert a thermometer in the soft
sediment and read a reasonably accurate temperature (in contrast to the
non-insulated water samplers). Because of the weight of sampler and cable, the
Clamm required a whale line “which are two and a half inches in circumference,
made of the best hemp, and very pliable and easily coiled”. For shallower seas
Ross advised: “for the North Sea, I would recommend one of fifty pounds”.

Also the Hydraphorus was an invention of John Ross (Appendix
XIII opus. cit.). The water sampler he received from Sir Humphrey Davy for the
work on board H.M.S Isabella failed “as its power was limited to 80 fathoms”.
The new instrument, only manufactured after the return of the ship, was made of
copper. The top part had an aperture to let the water in, which was covered by
a circular plate with a similar hole and with a toothed rim (800 divisions).
This plate was rotated by a vane when lowering the device in the water.
Pre-setting of the desired water depth where the sampler should operate was
thus possible.

Its size “intended for the expedition was 18 inches in
length besides the swivel, the circumference of the cylinder 15½ inches, the
whole weighing 78½ pounds, and intended to contain about 3 English pints of
water.” See e.g. McConnell, 1982[1];
Deacon, 1997[2]Kees Kramer

DESCRIPTION.
FIG. 2.

F — Section
of the machinery.

G — Upper
part or rope of the instrument.

E — The
instrument complete.

No.5
- Vanes of the rotator.

6 - Rotator with spiral wheel.

7 - First large wheel turned by the
rotator.

8 - Small wheel on the same axis, a.
No. 7.

9 - Second large wheel turned by No.
8.

10 - Swivel to which the rope is
attached.

11 - Spring air valve.

12 - Aperture in the wheel coinciding
with one in the cylinder to admit water.